1. Field of the Invention
This invention relates to grapples, and in particular to grapples used with power equipment for handling poles, such as electric power poles and telephone poles.
2. Prior Art
The term "pole" herein refers to any elongated, generally vertically disposed column, having a generally circular cross-section. Erection of poles, such as telephone poles and electric power poles usually requires, by reason of the fact that the poles have been notched and bored before they are installed, that the poles be set in a vertical position, but also be oriented so that cross arms and the like face in the proper direction.
In procedures heretofore developed for setting poles, the pole is usually suspended from an articulated boom of a hoisting machine by a rope, or the like, which is secured to the pole above its center of gravity. The pole when hoisted depends substantially vertically, and then with the assistance of a number of men at the butt end, the pole is jockeyed into position and lowered onto a support base or into a prepared hole with the butt end slightly clear of the bottom. The pole is rotated about its axis so that it is correctly oriented in azimuth and then lowered fully into the hole. The pole must then be placed in and held in an upright position while the hole is filled and tamped.
These operations require the use of a considerable number of men to control swinging movements and to position the pole while it is lifted and suspended, and to hold the pole upright during filling and tamping operations. Furthermore where long and heavy poles are being set, the operation can be quite hazardous due to the fact that the pole is hung freely from the machine boom and thus swinging movements cannot be fully controlled by the machine operator.